ix Electrical Circuits . . . . . . . . . . . . . . . . .104 Units of Electricity. . . . . . . . . . . . . . . . .105 Circuit Protection. . . . . . . . . . . . . . . 107 Switches, Relays, and Solenoids . . 108 Motorcycle Electronics . . . . . . . . . . 108 Diode. . . . . . . . . . . . . . . . . . . . . . . . . .108 Zener Diode . . . . . . . . . . . . . . . . . . . . .109 Thyristor . . . . . . . . . . . . . . . . . . . . . . . .109 Transistor . . . . . . . . . . . . . . . . . . . . . . .109 Thermistor . . . . . . . . . . . . . . . . . . . . . .109 Other Electronic Devices. . . . . . . . . . . .109 Sources of Electricity. . . . . . . . . . . . 110 Battery . . . . . . . . . . . . . . . . . . . . . . . . . 110 Magnetism . . . . . . . . . . . . . . . . . . . . . . 110 Motorcycle Wiring . . . . . . . . . . . . . . 111 Electrical Schematics and Symbols . . . . . . . . . . . . . . . . . . 112 Testing Electrical System Components . . . . . . . . . . . . . . . . . . 113 Multimeter . . . . . . . . . . . . . . . . . . . . . . 114 Other Testing Devices . . . . . . . . . . . . . . 115 Basic Electrical Diagnostic Methods . . . . . . . . . . . . . . . . . . . . . . 116 Using Test Equipment in Troubleshooting. . . . . . . . . . . . 117 Measuring Voltage . . . . . . . . . . . . . . . . 117 Using a Voltmeter in Diagnosis . . . . . . . 117 Measuring Resistance. . . . . . . . . . . . . . 118 Using an Ohmmeter in Diagnosis . . . . . 119 Measuring Current . . . . . . . . . . . . . . . .120 Electrical System Service and Repair. . . . . . . . . . . . . . . . . . . . 120 Soldering . . . . . . . . . . . . . . . . . . . . . . .120 Heat-Shrink Tubing . . . . . . . . . . . . . . . . 121 Crimp Connectors and Terminals. . . . . . 121 Electrical Service Precautions . . . . . . . .122 Chapter 8 Engines . . . . . . . . . . . . . . . 125 Engines . . . . . . . . . . . . . . . . . . . . . . . . 125 Four-Stroke Engine . . . . . . . . . . . . . 126 Four-Stroke Engine Operation . . . 127 Intake Stroke. . . . . . . . . . . . . . . . . . . . . 127 Compression Stroke . . . . . . . . . . . . . . . 128 Power Stroke . . . . . . . . . . . . . . . . . . . . 128 Exhaust Stroke . . . . . . . . . . . . . . . . . . . 128 Valve Overlap . . . . . . . . . . . . . . . . . . . .129 Four-Stroke Engine Components . . . . . . . . . . . . . . . . . . 130 Valve Train . . . . . . . . . . . . . . . . . . . . . .130 Pistons, Crankshafts, and Cylinders. . . .135 Engine Crankcase. . . . . . . . . . . . . . . . . 141 Two-Stroke Engine. . . . . . . . . . . . . . 144 Two-Stroke Engine Operation . . . 145 Two-Stroke Engine Components . . . . . . . . . . . . . . . . . . 146 Intake Timing . . . . . . . . . . . . . . . . . . . .146 Transfer and Exhaust Timing . . . . . . . . . 149 Crankcase Sealing . . . . . . . . . . . . . . . . 149 Crankshaft Confi gurations. . . . . . . . . . .150 Piston and Ring Design. . . . . . . . . . . . . 151 Cylinder Ports. . . . . . . . . . . . . . . . . . . . 152 Vertically and Horizontally Split Crankcases . . . . . . . . . . . . . . . .154 Two- and Four-Stroke Engine Power Characteristics . . . . . . . . . 154 Work and Energy . . . . . . . . . . . . . . . . .154 Torque and Power. . . . . . . . . . . . . . . . .154 Horsepower . . . . . . . . . . . . . . . . . . . . .154